Stabilization of the Output Power of a 20-Mw Klystron to within 0.1-Percent

For operation of a free electron laser, requirements on electron energy stability are extremely tight. When a radio frequency field is used to accelerate the electrons, this leads to stringent requirements on the stability of the klystron output power. We present results obtained with a 20-MW klystron which is energized by a pulse-forming network. The achieved stability of the klystron power is better than 0.1% during 20 mus.